Power over Ethernet (PoE) is a technology using a twisted pair to both transmit Ethernet data and supply electric power. The electric power refers to supplied electricity.
According to specifications of the Telecommunications Industry Association (TIA)/Electronic Industries Alliance (EIA) 568 (TIA/EIA-568), in an Ethernet twisted pair, a cable connected to a pin 1 (a cable 1 below) in an 8 position 8 contact (8P8C) modular connector and a cable connected to a pin 2 (a cable 2 for short below) in the 8P8C modular connector form a cable pair 3; a cable connected to a pin 3 (a cable 3 for short below) in the 8P8C modular connector and a cable connected to a pin 6 (a cable 6 for short below) in the 8P8C modular connector form a cable pair 2; a cable connected to a pin 4 (a cable 4 for short below) in the 8P8C modular connector and a cable connected to a pin 5 (a cable 5 for short below) in the 8P8C modular connector form a cable pair 1; a cable connected to a pin 7 (a cable 7 for short below) in the 8P8C modular connector and a cable connected to a pin 8 (a cable 8 for short below) in the 8P8C modular connector form a cable pair 4.
A PoE device includes two types of devices: power sourcing equipment (PSE) and a powered device (PD), or a PoE device may be both PSE and a PD. The PSE is a device that supplies electric power to the PD. The PD is a device that receives electric power, for example, an Ethernet device such as an Internet Protocol (IP) phone, a network camera, a wireless access point (WAP), a personal digital assistant (PDA), or a mobile phone charger.
Conventional PSE supports only two cable pairs in power supplying. For example, the PSE uses only the cable 1, the cable 2, the cable 3, and the cable 6 in the Ethernet twisted pair to supply power, or uses the cable 4, the cable 5, the cable 7, and the cable 8 in the Ethernet twisted pair to supply power. For example, if the PSE uses the cable 1, the cable 2, the cable 3, and the cable 6 in the Ethernet twisted pair to supply power, the PSE sends a detection signal to a peer end. When the PSE detects that a resistance and a capacitance of the peer end fall within a set range, for example, when the resistance falls within a range from 19 kilohms to 26.5 kilohms (kΩ) and the capacitance is less than 0.150 microfarad (μF), the PSE determines that the peer end is connected to a valid PD. The peer end is an end of the Ethernet twisted pair other than the other end connected to the PSE.
Classes negotiated between the PSE and the PD are classes 0 to 4. Power provided by the PSE is maximum in case of the class 4, and output power is approximately 30 watts (W). When power required by the PD is greater than 30 W, the PSE that supports only two cable pairs in supplying power cannot meet a requirement of the PD, and the PSE needs to use four cable pairs to supply power, that is, use both a first group of cable pairs and a second group of cable pairs to supply power to the PD. The first group of cable pairs include the cable pair 2 and the cable pair 3, and the second group of cable pairs include the cable pair 1 and the cable pair 4.
However, currently, if the PSE needs to use four cable pairs to supply power, there is no way to determine a status that a peer end is connected to a PD. As a result, power cannot be supplied, according to the status that the peer end is connected to the PD, to the PD connected to the peer end.